1. Field of the Invention (Technical Field)
The invention relates to an apparatus for protecting pipes, conduits, tubes, and the like against damage resulting from excessive pressures therein, particularly expansion damage due to the freezing of aqueous solutions contained therein.
2. Background Art
A number of efforts have been undertaken to fashion an apparatus or method whereby pipes and conduits may be protected against the damage resulting from the expansion of freezing water or aqueous solutions in the pipes or conduits. It has long been known that water, especially standing water, within closed pipes will expand upon freezing. As water undergoes the phase shift from liquid to solid, it expands in volume; crystal lattices of solid ice occupy substantially more volume than an equal weight of liquid water. When such expansion occurs within the confines of a closed tube, tremendous pressures are exerted radially outward against the interior wall of the tube. If unrelieved, such pressures can split or fracture the tube, resulting in damages that can be very costly to repair. Repairs can be particularly difficult if the damaged tube or pipe is located within a confined space, under a concrete slab, or within a wall, or the like.
U.S. Pat. No. 318,856 to Bilz, entitled Water Pipe, discloses a pipe having a liner fashioned from a series of ring-shaped sections of cork. U.S. Pat. No. 596,062 to Firey, entitled Device for Preventing Bursting of Freezing Pipes, discloses the use of a rubber or hollow metallic core mounted with flanges within a length of straight pipe. U.S. Pat. No. 1,643,021 to Luyties, entitled Construction of Pipes and the Like, discloses a pipe having a compressible liner made of a binder and filler mixture, such as asphalt and ground cork. The liner is applied to the pipe prior to the installation of the pipe. U.S. Pat. No. 2,629,402 to Cook, entitled Antiburst Tube for Pipes, discloses a tube, composed of a plurality of discrete compressible cells linked in series. U.S. Pat. No. 2,852,033 to Orser, entitled Anti-Surge Assembly, showing a device incorporating a resilient material to ameliorate the effects of pressure fluctuations in hydraulic assemblies. U.S. Pat. No. 3,665,967 to Kachnik, entitled Supercharge Hose, shows a fluid-carrying conduit surrounded by a body of resilient material adapted to absorb undulations of the conduit caused by pressure changes within the conduit. U.S. Pat. No. 4,651,781 to Kandelman, entitled Distributed Accumulator, discloses an inner conduit and outer conduit and compressible material disposed in the region between the conduits to absorb shock waves resulting from pressure changes in the inner conduit. U.S. Pat. No. 4,773,448 to Francis, entitled Freeze-Resistant Plastic Pipe and method for its manufacture, shows a method for simultaneously extruding a hard outer pipe shell and a soft resilient pipe liner to form a lined pipe. United Kingdom Patent Application No. GB 2,115,488A to Christie, et al., entitled Pressure Surge Attenuator, shows a thin walled inner pipe surrounded by a hard outer housing, with crushable metal foam disposed between inner pipe and outer housing to absorb pressure surges in the inner pipe.